1. Field of the Invention
The present invention relates to a structure of a thin battery covered by an outer packaging film, a battery pack, and method for manufacturing a battery pack to be used for a battery of a mobile phone, a game machine, a notebook-type personal computer, or the like.
2. Description of Related Art
As a battery structure and a battery pack, the one as shown in FIG. 10 is known. A battery pack 101 is constructed of a rectangular battery main body (referred to as a “battery cell” below) 103 containing power generation elements therein, and a circuit board unit 105 on which a plurality of electronic components 104 is mounted to constitute a protection circuit, which are accommodated in a battery case 102 constituted by two halves of a thin box. It is to be noted that, as shown in FIG. 11, the circuit board unit 105 is supported by ribs 106 formed on the battery case 102 so that the electronic components 104 do not contact the battery cell 103. As shown in FIG. 12, it has been also known a battery pack that eliminates the need for the ribs 106 in such a manner that a mold resin layer (referred to as a “transfer mold” below) 110 for molding the electronic components 104 is formed, a flat surface 110a at the end of the mold resin layer 110 is made to contact with a flat surface 103a of the battery cell 103, and they are accommodated in the battery case. (see, for example, Patent Document 1: Japanese Patent Application Publication No. 2002-110121 (in paragraphs [0003] and [0006], FIG. 2, FIG. 5, FIG. 6 and the like.))
The conventional battery pack 101 as described above has, however, the following drawbacks.    (1) Since the conventional battery pack 101 is constructed to accommodate the rectangular battery cell 103, and the circuit board unit 105 on which a plurality of electronic components 104 is mounted to constitute a protection circuit in the battery case 102 constituted by two halves of a thin box, the battery pack 101 becomes thick, bulky and heavyweight. Further, its cost is also high. In particular, the battery cell 103 tends to increase its thickness by swelling at the center portion thereof at the time of charging or in high temperature. It is therefore required to design the size of the battery case 102 with taking the inflation of swelling the battery cell 103 into consideration, thereby requiring a space between the battery case 102 and the battery cell 103 for absorbing such inflation. This makes the battery case 102 relatively large and is usually a cause of volume ratio deterioration of the battery cell 103 in the battery pack 101.    (2) In case of eliminating the need for the ribs 106 by contacting a flat surface 110a at the end of the transfer mold 110 molding and protecting the electronic components 104 with a flat surface 103a of the battery cell 103, there causes more or less adverse effects on the electronic components 104 or the like if the transfer mold 110 is pressed hard onto the battery cell 103.